Viscosity regulator



Nov. 2-2, 1949 B. N. HOFFSTRCM 2,489,136

VISCOSITY REGULATOR Filed Jan. 11, 1945 2 Shets-Sheet 1 Nov. 22, 1949 B. N. HOFFSTRCM 2,489,135

VISCOSITY REGULATOR Filed Jan. 11, 1943 2 Sheetsh t 2 Patented Nov. 22, 1949 VISCOSITY REGULATOR Bo N. Hoifstriim, Malmo, Sweden, assignor to A.-B. Aerotransport, Stockholm, Sweden, a corporation of Sweden Application January 11, 1943, Serial No. 472,083 In Sweden November 29, 1941 Section 1, Public Law 690, August 8, 1946 Patent expires November 29, 1961 7 Claims.

The present invention refers to an improved regulator for controlling the viscosity of a flowing medium, such as lubricating oil in engines.

For the purpose of controlling the viscosity of a medium such as oil, it is well-known to employ a thermostat regulator controlling a valve device which adjusts the composition of the viscous medium to maintain the viscosity at a predetermined value. In this case it is the temperature of the medium that determines the function of the valve device, and not the viscosity in itself. The calibration of the valve device in respect of the viscosity is then valid for a certain medium of a constant composition only.

It has been recognized as desirable to provide viscosity regulators in which the valve device is controlled in direct response to the viscosity of the medium and which will therefore be capable of being used for various kinds of media without recalibration. Thus, it has been proposed to control the valve device by means of the drop of pressure in a friction channel provided in the path of the medium, said drop of pressure varying as a function of the viscosity of the medium.

However, up to now there has been no reliably operating regulator of this kind.

The main object of the present invention is to provide an improved viscosity regulator of the last mentioned type through which a valve device is controlled in direct response to the viscosity of the flowing medium by utilizing the drop of pressure in a friction channel through which the medium is caused to pass.

It is a further object of the invention to provide a viscosity regulator of the type referred to in which the drop of pressure in the friction channel, which is a function not only of the viscosity but also of the velocity of flow of the medium through it, is supplemented by a drop of pressure in another channel or passage through which the medium is caused to flow, this channel or passage being such that the drop of pressure of the medium in it is a function of the velocity of flow of the medium only, this second drop of pressure being utilized for neutralizing the effect on the operation of the regulator of variations in the drop of pressure in the friction channel due to variations in the velocity of flow.

It is a still further object of the invention to provide a viscosity regulator of the type referred to which may be connected in a closed'circulation system, c. g. the lubricating system of an internal-combustion engine, in series with the crankshaft bearings of an engine, which consume the main part of the pressure obtaining in the system, so that the body of the circulating medium passes through the regulator and the drop of pressure in the latter can be directly used for controlling the valve device, i. e. no hydraulic by-pass resistance is needed for producing a controlling pressure.

The viscosity regulator according to the invention may be employed in conjunction with a valve device which proportions either two branch currents of a medium which respectively run to and by-pass a heat exchanger, or two mixture components delivered to a mixer, so that a predetermined viscosity is maintained or established in the medium after mixing the branch currents or components, respectively.

Other objects and features of the invention will appear from the following description.

The invention will be described in detail with reference to the accompanying drawings, wherein:

Figure l is a diagrammatic view of a viscosity regulator which is associated with a valve device and intended to be connected in the oil outlet from an internal-combustion engine;

Figure 2 illustrates, in longitudinal section, a form of the regulator which is intended to be connected either in the oil inlet or in the oil outlet from an engine and to control a separate valve connected in the outlet;

Figure 3 is a transverse section along the line IIIIII in Figure 2;

Figure 4 illustrates, in longitudinal section, another iorm of the regulator intended to be used in a similar way as the preceding one;

Fig. 5 is a diagrammatic view illustrating the connection of the regulator with a servo-motor and an oil cooler in an oil circulating system.

With reference to the regulator diagrammatically shown in Figure 1, it consists of a cylinder l which at its top is connected with the oil outlet of the engine (or with a return oil pump) and at its bottom opens into the interior of the housing of a valve device 2. In the cylinder I, a friction body 3 is inserted which consists of a number of juxtaposed tubes, so that the body is passed by many narrow channels in which the oil flowing through them is subjected to a friction resistance. Above the friction body 3 a constricting flange 4 is mounted in the cylinder. The Valve device 2 comprises two firmly interconnected pistons 5 and 6 of different areas which are movable in corresponding cylindrical porprincipal elements of the system, such as the tions of the valve housing. Behind the piston 6 a spiral spring 1 is provided which tends to press the pistons to the left. The pistons each cooperate with a port in the valve housing, and these ports are connected with conduits 8 and 9, respectively, of which the former leads to an oil cooler (not shown) and the latter leads to a point of the oil circuit beyond the cooler, e. g. directly to the oil tank. From a point of the cylinder l between the constricting flange 4 and the friction body 3 a conduit l leads to the valve housing 2 behind the piston 5, and from a point above the constricting flange 4 another conduit l I leads to the valve housing behind the piston 6.

For overcoming the friction resistance in the body 3 a certain drop of pressure p of. the flowing oil is required. This drop of pressure is a function of the viscosity of the 0111 and further a substantially linear function of the oil quantity which is flowing through. Also in the constricting flange B a drop ofpressure p" is produced which is a function of the second degree of the Velocity of the oil, i. e. the oil ,quantity, but on the "other hand is substantially independent of the viscosity of the oil.

Assuming the areas of the pistons 5 and 6 to be a and b, respectively, the forces exerted on the pistons by the oil are P1=p.a P2: (p+p") b where P1 is the force acting on piston 5 and P2 the force acting on piston 6, and if the force of the spiral spring I is F, then in the case of equilibrium P1P2=F If the viscosity of the oilincreases over a desired average value Pi increases more than P2, and the pistons are pressed to the right, the conduit 8 to the cooler being shut off-and the by-pass conduit 9 being more opened. On the other hand, if the oil becomes thinner-and the viscosity lower than the average value, the pistons move to the left in a corresponding manner, the conduit 9 being shut off'more or'less and'the conduit 8 being opened.

Thus, the position of the pistons will bea function of the viscosity-of-the oil. Thishowever takes place only when, as here assumed, a spring is used for balancing the'forces on the pistons produced by the drops of pressure. is omitted, it is certainly possible to attain a displacement of the pistons" owing to variations of the viscosity, but this displacement can take place only'in' the form of asudden change from one to the other of the end positions of the pistons as P1 or P2 predominates.

The operation of the regulator can be made independent of the velocity of the oil by suitably proportioning-the piston areas a and b in relation to each other. This will be shown by the following mathematicalconsiderations.

The condition of equilibrium or, if

by definition,

The two pressure differentials p and p can be expressed as functions of the velocity of the oil by the equations p=k1.u|-'N If the spring which is a form of Poiseuilles law of the flow of viscous fluids through capillaries, it being the velocity of the oil, k1 a factor proportional to the viscosity of the fluid and to the length of the narrow. channels in the body3 and inversely proportionalto' the area of said channels, and N an empirical term dependent on the nature of the fluid and the geometrical dimensions of the channels and p =kz.u

which is a form of Bernoullis equation rendering the relation between the drop of pressure of a fluid flowing in a conduit of variable cross-sectionand the velocity of said fluid, k2 being a factor dependent on the density of the fluid but independentof the viscosity thereof.

In view of the above explanation of the factor In, the relation between it and the viscosity y may be expressed as where k; is a factor independent of the viscosity but dependent on the dimensions of the friction channels.

Hence,

Pf=(kf.'y.u+N) (ab) Ps k2-u .b

These expressions show that Pf is a force which is dependent both on'the velocity and on the-viscosity of the oil and-PS is a force which is dependent on the velocity of the oil but independent of the viscosity.

It will be seen that the equation of. equilibrium can be valid only at a certain value of the viscosity for which the regulator-has been calibrated. -Pr and PS always acton the pistons in opposite directions, and Pf is greater than P5, the difference being balanced by the auxiliary force F. If the viscosity changes, only the term Pi is altered while PS and F remain unchanged. The system is thus unbalanced anda free force, theregulating force,

arises. 1 On the other hand, if the viscosity is held where um isan averagevalue of uwithin the range of velocities in which the regulator normally operates. Hence,

It will be seen that the relation whichisafixed quantity for a given design, has

to be selected. for adesired value of the velocity u.

When operating withina limited-range on either side of the average velocity mm, the deviation which naturally results in a slight Variation of the value of the viscosity for which the regulator is adjusted is of no practical importance.

The last equation can also be written When designing the regulator three of the quantities a, b, In and ice are first determined. If, for example, the design of the friction body 3 and the constricting flange 4 has been laid down, R11 and 702 can be determined empirically, either a or b may be chosen at will and the fourth quantity, i. e. b or a, is determined so as to satisfy the above condition.

In Figures 2 and 3 a practical form of the viscosity regulator is shown. The regulator comprises an internally cylindrical body I2 having two unequal inner cross sectional areas and a fitting I3 containing a valve slide I4 and connected with the member I2 in axial alignment thereof through an outer conjoining housing I5 which is formed with an inlet piece I6 for the oil. Inside the housing I5 and between the cylinder body I2 and the fitting I3 there is provided a cylindrical oil filter H which encloses a space I8. In this space the oil is under a predetermined pressure which is produced for example by means of a pump connected in the inlet conduit connected with the piece I6.

The cylinder body I2 is itself composed of two axially disposed principal parts, of which the part I9 which is turned towards the fitting I3 has the larger inner cross sectional area and the other part includes a cylindrical socket 2| which is closed at its outer end and has the smaller cross sectional area. The part 20 has an outer jacket 22 which surrounds a space 23 situated between the inner part I9 and the socket 2| and connected by ports 24 with a space or a conduit outside the regulator.

The cylinder part |9 having the larger cross sectional area has a friction body 25 fastened by screwing in the end turned towards the fitting I3. This friction body consists of a tube which -is provided with a threaded shoulder for the fastening of it by screwing and the interior of which is filled with a number of narrow tubes 26 so that there are formed many narrow channels through which the oil must flow (Figure 3). In the cylinder body I2 a differential piston 21 is slidable, in that it has two parts of different cross sectional areas which fit within the respective cylindrical portions I9 and 2| of the body I2.

The piston part movable in the cylinder part I9.

is formed as a cup having its hollow turned downwards towards the interior of the regulator, and in its wall there are made a number of constricting ports 28 forming passages for the oil coming from the friction body 25 to the space 23. The differential piston 21 is firmly mounted on an axially bored piston rod 29 which extends through the friction body 25 and cooperates at its inner end with the valve slide I4. Through a radial hole 30 the boring in the piston rod communi-= 'cates with the space I8 inside the oil filter I1,

and th pressure of the oil which fills this space is thus transmitted through the piston rod to oil which stands in the cylindrical socket 2| and acts on the smaller area of the piston 21 in the opposite direction to the oil which has passed through the friction body 25 and acts on the larger area of the piston.

The fitting I3 is formed as a slide valve device.

Its valve slide I4 is arranged in a boring 3| in.

axial alignment with the piston rod 29 and is held pressed against the end of the latter by a spiral spring 32 which is provided in a boring 33 in the outer end of the fitting I3 and is tensioned between a screw plug 34 and a shoulder disc 35 on the valve slide. On the end projecting into the interior of the regulator the valve slide I4 has a slide surface 36 which seals against the wall of the boring 3|, and nearer the outer end it has another slide surface 31 which cooperates with an annular turned groove 38 in the fitting I3. In the normal position of the valve slide the slide surface 31 shuts off the groove from communication with the boring 3| in one as well as in the other direction. The turned groove communicates through a channel with a threaded hole ,39 in the fitting intended for the connection of a conduit 39a (Fig. 5) which leads to a servo-motor. Furthermore, at a point on the inner side of the turned groove 38 the boring 3| communicates through a channel 4|] with another threaded hole 4| in the fitting I3 for the connection of a conduit 4m (Fig. 5) leading to an accumulation station for the oil, preferably the oil sump of the engine. The valve slide I4 has an axial channel 42 which communicates at its inner end with the space I8 within the oil filter I1 and opens at its outer end into the boring 33. The pressure in the space I8 is thereby transmitted to the boring 33, so that it will act on the valve slide from both directions. Oil under pressure which enters into the boring 33 through the axial channel 42 can penetrate into the outer portion of the boring 3 I, in that the disc 35 is provided with apertures 43 to allow this. Oil under pressure passes from the space I8 through the channel 42 into the boring 33, then through the apertures 43 in the disc 35 to the upper side of the latter, and the space above the disc 35 is in direct communication with. the lower part of the boring 3| (under the slide portion 31) When the valve slide occupies its upper position, the oil can further flow through the turned groove 38 to the conduit connected at 39.

Fig. 5 illustrates how the regulator described above is connected with a servo-motor and an oil cooler in an oil circulating system. It is to be understood that the servo-motor can be of any suitable kind which can control a valve in the oil outlet conduit from the engine, so that the valve varies the proportions of the oil which runs to and by-passes the oil cooler, respectively; the servo-motor diagrammatically shown in Fig. 5 is intended only to illustrate the principal mode of operation thereof and is not to be construed as an actual structure.

The viscosity regulator according to Figure 2 is preferably to be connected in the oil inlet conduit of the engine as indicated in Fig. 5. The oil is pumped in from the tank through. the inlet I6, passes through the oil filter I'I into the space I8 and after that flows first through the friction body 25, then through the constricting ports 28 and finally through the ports 24 further to the engine. The drops of pressure p and p hereby created in the friction body 25 and the constricting ports, 28, respectively, produce on the differential piston 21 a resulting force which at normal oil viscosity is to be in equilibrium with the spring 32. By an analysis corresponding to that given above for Figure 1, it is found that if the viscosity of the oil increases above a desired average value, the differential piston 21 will be pressed downwards in Figure 2 and displace the valve slide I4, so that oil from the servo-motor can flow in at 39, through the boring 3| and the channel and out at, the servo-motorbeing adaptedtoadjust the'control valve in'thaoil outlet conduit from the engine, so that a-larger proportion of the oil by-passes the cooler. If,-on the other hand, the viscosity decreases; the'differential piston 21 is displaced upwards in -Figu're 2,the spring 32 pushing the valve slidei4 up'wards, so that oil under pressure from the main current through the regulator can be divertedthrough thechannel 42, the boring'tsan'd the connection 39 to the servo-motor, while the first mentioned communication between the connections 39 and 4| is shut off. The servo-motor now adjusts the control valve in such amanner that more oil is led throughthe' cooler. 'The relation between the areas of the 'difierential piston has been determined on the basis of the same analysis as in respect of Figure -1, so that the influence of the oil quantity has been eliminated.

The viscosity regulator i-l-lustrate'd in Figure 4 does not differ in principle irom'that described above except in'so far as itoperatesw ith a continuous flow of oil through the valve device. Similarly as in Figure 2, the'regulator consists of a cylinder body'44 and a fitting 45 containinga valve, said parts being held together by an'outer housing 46 which is provided with an inlet piece 41 for oil under pressure. Within thehousing 46 and between the'p'arts 44 and 45 there is provided a cylindrical oil filter 48 which encloses a space 49 containing oil underpress'ure.

The cylinder body 44 comprises a cylindrical socket 56 closed at its outer end and an outer jacket which is'concentric' with this socket and encloses an annular spac 52 which is -connected by ports53 with a space or a conduit-outside the regulator. An outer fiangering 54 is provided for carrying the cylinder body and forminga support for the filter cylinder-48.

In the inner end of the 'j a'cket 5l which is turned 2 towards the fitting 45 a friction body 55 -'is screwed. This-consists ofa cylinder which'co'ncentrically encloses another cylinder 56 of a smaller diameter. If desired, several such'cylinders may be provided concentrically withineach v axially inward-turned cylindrical fia-nge' 59-with which the piston can engage the adjacent end of the tube 51 for limiting the stroke in the inward direction. The cylindrical flange 59' extends through the opening of an annular disc 66 which is placed against a shoulder within thee,

jacket 51 where it is held by the cylinder 55. 'The space 59a between the fiange'59 and the ring= 6il forms a narrow passage for the oil corresponding to the aperture in the constricting flange 4 in Figure 1 or the ports" 28 -in thedifie'rentialpis'ton in Figure 2. This passage is in alignment with the channels in the friction body'5'5, so that the oil can fiow through it without altering 'itsdirection. It will be particularly pointed out that the flow of oil does not act on any of-the surfaces 5;

of the differential piston as in Figure 2, so" that there need never be any question of a correction --with regard to dynamic pressure. Theidiiferential piston 58 is firmly mounted on. an axially bored piston rod 6l which extends down through its ' Icy-passes the cooler.

'' above, andtherefore it is not to be considered limited to these.

-is' in communication with the surrounding space through a radial hole 66, the pressure of the oil which fills the space 49 within the oil filter 48 is transmitted to the oil which stands in the cylindrical socket 50. This pressure will thus 'act on-the smaller area of the piston in the opposite direction to the pressure on the larger area of the piston of the oil whichhas passed through the friction body 55. A spiral spring 14 is provided within thetube 51 between the partition N-and the differential piston 58 to exert an up- "ward pressure on the piston.

"The conical-valvemember 62 which is formed on ashank fastened to the end of the piston rod 61 is slidably mounted in a boring 61 in a socketshaped member 68 which is placed over an axial boss-69 onthe inner side of the fitting 45 and is surrounded by the tube 51. The boring 61 is formed with a seat for the conical valve member '62 whichis arranged so that the passage is shut on at the upward movement'of the piston in Figure 4. The fitting45 has throughout its length an axial boring 1B which at its outerend is formed with a threaded connection 1| for a conduit equivalent to conduit 39a in Fig. 5 and leading to the servo-motor. In the" fitting 45 there is further made a narrow channel 12 which issuing from the boring 10 opens into a threaded hole 13 in "the side of the fitting for connecting a conduit equivalent to conduit 4la' in Fig. 5 and leading to the accumulation station for the oil.

"The valve member 62 is so arranged in relation to theseat in the boring 61 that it stands in an intermediate position when the 'oil flowing through the regulator has normalviscosity. A

minor proportion ofthe oil standing under pressure in'the spaces 49- and 65 thus continuously flows past the conical valve member 62 to the boring 10 and further through the narrow channel 12 to the accumulationstation for the oil. On this account there obtains in-the boring and thereby in the servo-motor a certain lower pressure than in the spaces 49 and 65, the servoarea of the conical valve is increased. On this account the pressure in the boring 10 increases, which causes a movement of the servo-motor in such a direction that a larger proportion of the oil If, on the other hand, the viscosity becomes lower, the valve' passage area decreases the pressure in the boringlll being reduced and theservo-motor moved in the reverse direction.

The inventioncan be carried into effect in a plurality of other forms than those described Moreover, the invention isnot' limited to the control of theviscosity of lubricating oil but can advantageously -'be applied wherever it is a ques- 9 tion ofkeeping the viscosity of a viscous medium constant. a

What I claim and desire to secure by Letters Patent is:

1. In an apparatus responsive to the viscosity of a continually circulating medium in a main flow conduit, a housing interposed in the main conduit and defining a path of flow of the medium through a portion of said conduit, a friction channel body including a numberof parallel narrow friction channels and mounted within said housing in said path, orifice means provided within said housing and connected in series with said friction channel body in said path, a differ ential piston having areas exposed to the pressures respectively before, between and after said friction channel body and said orifice means so as to respond differentially to the pressure differentials set up across said friction channel means and said orifice means as a result of the flow of the medium therethrough.

2. In an apparatus responsive to the viscosity of a continually circulating medium in a main flow conduit, means interposed in the main conduit and defining a path of flow of the medium in said conduit, friction channel means in said path, orifice means connected in series with said friction channel means in said path, a differential piston having areas exposed to the pressures respectively before, between and after said friction channel means and said orifice means so aS to respond differentially to the pressure differentials set up across said friction channel means and said orifice means as a result of the flow of the medium therethrough.

3. In an apparatus responsive to the viscosity of a continually circulating medium in a main flow conduit, a housing interposed in the main conduit and defining a path of flow of the medium in said conduit, cylindrical friction channel means provided within said housing in said path, orifice means provided within said housing and connected in series with said friction channel means in said path, a cylindrical hollow body mounted within said housing coaxially with said friction channel means, a differential piston movable in said hollow body and having areas exposed to the pressures respectively before, between and after said friction channel means and said orifice means so as to respond differentially to the pressure differentials set up across said friction channel means and said orifice means as a result of the flow of the medium therethrough.

4. In an apparatus responsive to the viscosity of a continually circulating medium in a main flow conduit, a housing interposed in the main conduit and defining a path of flow of the medium in said conduit, cylindrical friction channel means provided within said housing in said path, orifice means provided within said housing and connected in series with said friction channel means in said path, a cylindrical hollow body mounted within said housing coaxially with said friction channel means, a differential piston movable in said hollow body and having areas ex posed to the pressures respectively before, between and after said friction channel means and said orifice means so as to respond differentially to the pressure differentials set up across said friction channel means and said orifice means as a result of the flow of the medium therethrough, a piston rod associated with said differential piston and arranged coaxially within said friction channel means, said piston rod having an axial boring connecting the interior of said housing at the input side of said friction channel. means and said orifice means with a space in said hollow body for transmitting the pressure of the medium to a face of said differential piston bounding said space.

5. In an apparatus responsive to the viscosity of a continually circulating medium in :a main flow conduit, means interposed in the main flow conduit and defining a path of flow of the medium through a portion of said conduit, friction channel iiow, controlling means in said path, orifice fiow controllin means connected in series with said friction channel flow controlling means, movable means differentially responsive to pressure differentials set up across both of said flow controlling means on one hand and across one of said control means on the other hand, as a result of the fio-w of medium therethrough, and valve means operative in response to the operation of said movable means and connected in the path of flow of a hydraulic servo medium for controlling the viscosity of the continually circulating medium.

6. An apparatus for regulating the viscosity of a continually circulating medium in a main flow conduit comprising means interposed in the main conduit and defining a path of flow of the medium in said conduit, friction channel flow controlling means in said path, orifice flow controlling means connected in series with said friction channel flow controlling means, movable means differentially responsive to pressure differentials set up across both of said flow controlling means on one hand and across one of said control. means on the other hand as a result of the flow of the medium therethrough, a branch path for said medium, valve means actuated by said differentially responsive means and controlling flow of medium from said path into said branch path of the medium for establishing pressure variations therein depending on the response of said differentially responsive means, and means responsive to pressure of the medium in said branch path for adjusting the viscosity of the medium in the main conduit according to said response.

'7. An apparatus for regulating the viscosity of a continually circulating medium in a main fiow conduit comprising means interposed in the main conduit and defining a path of flow of the medium in said conduit, friction channel flow controlling means in said path, orifice flow controlling means connected in series with said friction channel flow controlling means, movable means differentially responsive to pressure differentials set up across both of said flow controlling means on one hand and across one of said control means on the other hand as a result of the flow of the medium therethrough, a branch path for said medium means enclosing a space which is inter posed in said branch path of said medium, valve means inserted in said branch path and actuated by said differentially responsive means, and means forming a constricted channel interposed in said branch path in series with said space and said valve means in such a way that said space is situated between said valve means and said channel, the arrangement being such that said valve means allow a continual flow of the medium through said branch path in a condition of said differentially responsive means corresponding to normal viscosity of the medium, said valve means in its operation causing pressure variations in said space depending on the response of said differ- REFERENCES CITED.

7 The following references are of record in the file'of this patent:

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